package network;

import sun.dc.pr.PRError;

import java.io.IOException;
import java.net.*;
import java.util.Scanner;

public class UdpEchoClient {
    private DatagramSocket socket = null;
    private String serverIp = "";
    private int serverPort = 0;

    public  UdpEchoClient(String ip, int port) throws SocketException {
        // 创建这个对象,不能手动指定端口
        socket = new DatagramSocket();
        // 由于UDP自身不会持有对端的信息,就需要再应用程序中把对端的信息给记录下来
        // 这里记录的是对端的ip和端口号
        serverIp = ip;
        serverPort = port;
    }

    public void start() throws IOException {
        System.out.println("客户端启动!");
        Scanner scanner = new Scanner(System.in);
        while(true){
            // 1. 从控制台读取数据,作为请求
            System.out.print("->");
            String request = scanner.next();
            // 2. 把请求内容构造成 DatagramPacket 对象,发给服务器
            DatagramPacket requestPacket = new DatagramPacket(request.getBytes(),request.getBytes().length,
                    InetAddress.getByName(serverIp),serverPort);
            socket.send(requestPacket);
            // 3. 尝试读取服务器中返回的响应了
            DatagramPacket responsePacket = new DatagramPacket(new byte[4096],4096);
            socket.receive(responsePacket);
            // 4. 把响应转化为字符串,然后显示出来
            String response = new String(responsePacket.getData(),0,responsePacket.getLength());
            System.out.println(response);
        }
    }

    public static void main(String[] args) throws IOException {
        UdpEchoClient client = new UdpEchoClient("127.0.0.1",9090);
        client.start();
    }
}
